This invention relates to a low pressure, self-contained fire suppression system for Class A or Class B fires and other applications. The fire suppression system of this invention generates a fire suppression foam from foam concentrate, water and a gas such as air or nitrogen. The fire suppression system of this invention is self-contained in that it does not require connection to an external water, pressurized gas or power supply. The present system may be configured to be either portable or stationary.
Prior art devices used to generate a water/air fire fighting foam either used aspirated air in the foam generating unit or used a compressed gas under high pressure.
Aspirated type foam generators have a low foam expansion rate (a foam to foam solution volume ratio of between about 1:1 and 20:1), require a large amount of foam concentrate to develop foam (a minimum of 0.05% of foam concentrate in water, but more typically about 1.0%), and the foam generated does not have the durability of compressed air foam generators. Aspirated nozzles require high pressures to develop acceptable fire suppressant foam, generally requiring a minimum pressure of 100 psig.
Prior art compressed gas foam generators used compressed gas under a very high pressure of above 100 psig and as high as 300 psig. For example, the device disclosed in U.S. Pat. No. 3,977,474 utilizes gas at a pressure of 300 psig to pressurize a water reservoir tank. Such high pressures present a safety hazard for a single operator and would require several highly trained operators for safe operation. Such high pressure operation would deplete a reservoir type water supply very rapidly.
It is an object of the present invention to provide a low pressure, self-contained fire suppression system that can be safely operated by a single, untrained operator, that is user friendly (requiring the opening of only one valve to commence foam generation), that is easily recharged, and that is capable of generating a dry, fire suppressing foam for a substantial period of time.